The running science nerd alert.
September 2023
Learn to train smart, run fast, and be strong with Thomas Solomon PhD
Here are this month's latest research studies on running-related exercise and nutrition science.
The studies are divided into sub-topics — training methods, sports nutrition, supplements, recovery, athlete health, injuries, female athletes, and my beer of the month, etc. — so you can skip to what you’re interested in.
I’ve provided a brief statement about the conclusion of each study, but click on the study title to read the full paper.
Training methods.
Randomised controlled trial: Aerobic high-intensity intervals improve V̇O2max more than supramaximal sprint intervals in females, similar to males. Helgerud et al. (2023) Scand J Med Sci Sports 
“In aerobically well-trained women, high-intensity interval training is superior to sprint interval training in increasing V̇O2max while all-out treadmill running sprint interval training (10 × 30 s) induced an unacceptable rate of muscular strains, and it should therefore be carefully considered if applying this treadmill protocol is necessary.” Non-randomised trial: Peak Running Velocity vs. Critical Speed: Which One Is Better to Prescribe Endurance Training to Recreational Runners? Figueiredo et al. (2023) J Strength Cond Res “The main finding was that critical speed showed a higher correlation and predictive power for the 5-km running performance, slightly better than that of peak running velocity determined on the track, which is contrary to the initial hypothesis. Also, the critical speed values estimated through three time-trials and the combination of the shortest and the longest time-trials presented the highest correlation and predictive power for this performance in recreational runners.” Non-randomised controlled trial: Hemoglobin mass and performance responses during 4 weeks of normobaric “live high–train low and high”. Kettunenet al. (2023) Scand J Med Sci Sports “Four-week normobaric "live high-train low and high" was beneficial for increasing Hbmass but did not support the short-term development of maximal endurance performance and VO2max when compared to the athletes who lived and trained in normoxia.” Randomised controlled trial: Influence of exercise intensity and hypoxic exposure on physiological, perceptual and biomechanical responses to treadmill running. Tee et al. (2023) Eur J Sport Sci “Overall perceived discomfort at slower (8 km.h−1) and faster (16 km.h−1) speed and perceived difficulty breathing (at all speeds) were lower in moderate hypoxia than in severe hypoxia, whereas leg discomfort did not differ with hypoxic exposure. The possibility to use hypoxia therapeutically as a promising approach to eventually maintain or regain fitness in load compromised individuals requires future studies.” Randomised controlled trial: Evidence that heat acclimation training may alter sleep and incidental activity. Osborne et al. (2023) Eur J Sport Sci “Five consecutive days of heat training negatively affected some objective measures of sleep quality and incidental physical activity in recreationally trained athletes.Athletes and coaches need to be aware of the potential unintended consequences of using heat acclimation on sleep behaviours.” Randomised controlled trial: Reduced running performance and greater perceived exertion, but similar post-exercise neuromuscular fatigue in tropical natives subjected to a 10 km self-paced run in a hot compared to a temperate environment. Rodrigues Júnior et al. (2023) PLoS One “In conclusion, hot conditions impair endurance performance, enhance perceptual responses, and transiently changes physiological strain during a self-paced run compared to temperate conditions. Moreover, lower limb neuromuscular fatigue, determined by the reduction in countermovement jump height, is evident 1 h after the 10 km run. Despite the marked endurance performance impairment induced by exercise-heat stress, post-exercise neuromuscular fatigue is similar between temperate and hot conditions.”
Sports nutrition.
Randomised controlled trialt: Acute Ingestion of a Ketone Monoester without Co-Ingestion of Carbohydrate Improves Running Economy in Male Endurance Runners. Brady et al. (2023) Med Sci Sports Exerc “Acute ingestion of a ketone monoester without carbohydrate, but not when co-ingested with carbohydrate, improved running economy in middle- and long-distance runners at a range of submaximal running speeds, and did not alter time to exhaustion in a short duration ramp test to volitional exhaustion. Further investigation is required to examine if these differences translate into positive performance outcomes over longer durations of exercise.” Randomised controlled trial: A Menthol-Enhanced "Cooling" Energy Gel Does Not Influence Laboratory Time Trial Performance in Trained Runners. Vogel et al. (2023) Nutrients “Among recreationally trained runners, a menthol-enhanced energy gel did not provide superior performance or perceptual benefits during a 20 min time trial following 40 min moderate treadmill exercise in the heat compared to a non-menthol energy gel. More research is needed to confirm whether these findings are consistent in ecologically valid scenarios, such as outdoor competition in the heat, and among elite athletes.” Position stand: International society of sports nutrition position stand: energy drinks and energy shots. Jagim et al. (2023) J Int Soc Sports Nutr (multiple statements made; see full paper for details) Position stand: International society of sports nutrition position stand: coffee and sports performance. Lowery et al. (2023) J Int Soc Sports Nutr (multiple statements made; see full paper for details)
Supplements.
Systematic review and meta-analysis: Effects of citrulline on endurance performance in young healthy adults: a systematic review and meta-analysis. Harnden et al. (2023) J Int Soc Sports Nutr “The current evidence suggests no significant benefit of citrulline supplementation for endurance performance. However, the small evidence base requires further research to fully evaluate this topic.” Systematic review and meta-analysis: The Effect of Long Chain n-3 Fatty Acid Supplementation on Muscle Strength in Older Adults: A Systematic Review and Meta-Analysis. Timraz et al. (2023) Nutrients “The findings of our meta-analyses should be interpreted with caution due to several notable limitations. These include the limited number of studies and participants involved, as well as the presence of substantial heterogeneity across the included studies. This makes our conclusions tentative. Supplementation with LCn-3 PUFA seems to have a positive impact on muscle mass; however, its effect on muscle strength and function remains inconclusive. Therefore, additional research is necessary to determine if LCn-3 PUFA supplementation has utility as a strategy for preventing or treating age-related declines in muscle strength, mass, and functional abilities. Additionally, optimal dosing strategies should be investigated.” Systematic review and meta-analysis: Effect of Soy Protein Supplementation on Muscle Adaptations, Metabolic and Antioxidant Status, Hormonal Response, and Exercise Performance of Active Individuals and Athletes: A Systematic Review of Randomised Controlled Trials. Zare et al. (2023) Sports Med “This systematic review reveals that SPs may increase lean mass during resistance training similarly to whey protein; nevertheless, certain studies indicate that milk and whey proteins may be preferable for increasing lean mass at a faster rate. While soy protein supplementation in athletes/active individuals is promising, the studies included in the review have several limitations, such as heterogeneity of interventions, exercises performed, exercise intensities and frequency and timing of protein intake. Therefore, future studies adjusting total daily protein intake as ~ 1.6 g/protein, including both leucine-matched and dose-matched protein administration, and ≥ 12 weeks of training protocols along with the supplementation are needed.” Systematic review and meta-analysis: The impact of dietary protein supplementation on recovery from resistance exercise-induced muscle damage: A systematic review with meta-analysis. Pearson et al. (2023) Eur J Clin Nutr “In young males, peri-exercise protein consumption reduces maximal strength decrements and lowers [CK] following acute resistance exercise but does not benefit muscle soreness. These outcomes are seemingly unaffected by the type, timing, frequency, and dose of ingested protein, though may be affected by the exercise protocol and sample training status, with further examination required. This review identified an absence of female-focused research and a limited number of studies examining plant-based protein sources, which warrants future research priority. Developing evidence-based exercise-induced muscle damage management strategies is impeded by methodological inconsistencies across studies, particularly pertaining to EIMD assessment methods.”
Recovery (inc. sleep).
Randomised controlled trial: Effects of pre-sleep protein supplementation on plasma markers of muscle damage and inflammatory cytokines resulting from sprint interval training in trained swimmers. Wu et al. (2023) J Int Soc Sports Nutr “We provided trained swimmers with either a PRO or a CHO beverage of equal caloric value every night preceding going to bed while maintaining a standardized diet for as short as two weeks. Consumption of whey protein before sleep did not result in a decline in blood factors related to muscle damage or induce a systemic anti-inflammatory response.” Systematic review and meta-analysis: Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults. Singh et al. (2023) Cochrane Database Syst Rev “Blue‐light filtering spectacle lenses may not attenuate symptoms of eye strain with computer use, over a short‐term follow‐up period, compared to non‐blue‐light filtering lenses. Further, this review found no clinically meaningful difference in changes to critical flicker-fusion frequency (CFF) with blue‐light filtering lenses compared to non‐blue‐light filtering lenses. Based on the current best available evidence, there is probably little or no effect of blue‐light filtering lenses on best-corrected visual acuity (BCVA) compared with non‐blue‐light filtering lenses. Potential effects on sleep quality were also indeterminate, with included trials reporting mixed outcomes among heterogeneous study populations. There was no evidence from randomised controlled trial (RCT) publications relating to the outcomes of contrast sensitivity, colour discrimination, discomfort glare, macular health, serum melatonin levels, or overall patient visual satisfaction. Future high‐quality randomised trials are required to define more clearly the effects of blue‐light filtering lenses on visual performance, macular health and sleep, in adult populations.” Epidemiological observation: Hit the gym or hit the hay: can evening exercise characteristics predict compromised sleep in healthy adults? Miller et al. (2023) Front Physiol “Compared to avoidance of evening exercise (i.e., do not exercise in the evening), the current models allow for some evening exercise to be performed with only a small percentage of sleeps being compromised. Interpretations of the results should be made with boundary conditions in mind. Participants included in the study were physically active; it is unclear whether similar results would be obtained with less active individuals.”
Athlete health (inc. mental health).
Observational study: Nutritional intake and anthropometric characteristics are associated with endurance performance and markers of low energy availability in young female cross-country skiers. Kettunan et al. (2023) J Int Soc Sports Nutr “Anthropometric characteristics, especially body fat percentage, and training volume appeared to be the most important factors explaining different indicators of a young female cross country skier’s performance. In addition, lower carb and protein intake were associated with higher body mass, fat mass, and body fat percentage as well as with lower VO2max and double poling performance. Taken together, these findings suggest that although lean body composition may be beneficial for endurance performance, it should not be sought by restricting dietary intake. Indeed, athletes with lower carb intake and energy availability not only had poorer performance but also an increased risk of self-reported physiological symptoms of low energy availability. These findings highlight the importance of adequate energy availability and macronutrient intake to support performance and overall health.” Non-randomised controlled trial: The impact of natural menstrual cycle and oral contraceptive pill phase on substrate oxidation during rest and acute submaximal aerobic exercise. Williams et al. (2023) J Appl Physiol “This study was the first to examine the influence of natural menstrual cycle and two generations of oral contraceptive pills on substrate oxidation during rest and acute submaximal aerobic exercise. We reported no differences across cycle phases or groups on respiratory exchange ratio (RER), and minimal impact on carbohydrate or lipid oxidation apart from an increase in carbohydrate oxidation in natural menstrual cycle compared with 2nd generation oral contraceptive pills during exercise. Based on these findings, controlling for natural menstrual cycle/oral contraceptive pill phase may not be necessary for studies investigating substrate oxidation.” Review: Mental Health in the Specialized Athlete. Daley et al. (2023) Curr Rev Musculoskelet Med “Promoting the mental health and psychological wellbeing of specialized young athletes requires a multidimensional team-based approach, starting with the recognition that mental health is as important as physical health and that the two are inextricably linked, with significant implications for performance, recovery from injury, and long-term athletic success.”
Injury and rehab.
Observational study: Running towards injury? A prospective investigation of factors associated with running injuries. Dillon et al. (2023) PLoS One “Of the clinical factors, history of injury in the past year and less navicular drop were univariately associated with increased odds of injury. In terms of stance-based measures of running technique, knee, pelvis and hip motion in the frontal and transverse planes were associated with increased odds of injury. Anthropometrics, demographics, strength, range of motion and measures of impact acceleration were not significantly associated with injury. This study emphasises the multifactorial nature of running-related injuries and finds that factors remain outstanding that contribute to running-related injury development. Although these factors had a 74% accuracy in discriminating between injured and uninjured; the use of these variables as screening tests may have limited value.”
Female athletes and sex differences.
Position stand: International society of sports nutrition position stand: nutritional concerns of the female athlete. Sims et al. (2023) J Int Soc Sports Nutr (multiple statements made; see full paper for details) Observational study: Sex differences in fatigability and recovery following a 5 km running time trial in recreationally active adults. Pons et al. (2023) Eur J Sport Sci “During the time trial, females and males exercised at similar intensities, with equivalent heart rates and rating of perceived exertion (RPE), however, immediately following the time trial, less fatigue was observed in female knee extensors compared to males. Females also maintained greater relative maximal voluntary contraction (MVC) force up to 10 min post-exercise.”
And, to help you wash down the latest evidence, here's a snifter from my recent indulgence...
Beer of the month:
Mis-Thunder-Stood from Browar Stu Mostów (Poland).
Imperial pastry stout (ABV = 10.5%).
Rating of Perceived beer Enjoyment = 7/10 Hazelnut to the eye, molasses and chocolate to the nose, a sweet, full and almost bready mouth feel, smooth and chocolatey down the hatch, and a mildly boozy vanilla and bready aftertaste. Mis-thunder-stood leaves quite the impression.
Rating of Perceived beer Enjoyment = 7/10
Hazelnut to the eye, molasses and chocolate to the nose, a sweet, full and almost bready mouth feel, smooth and chocolatey down the hatch, and a mildly boozy vanilla and bready aftertaste. Mis-thunder-stood leaves quite the impression.
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Disclaimer: I occasionally mention brands and products but it is important to know that I am not affiliated with, sponsored by, an ambassador for, or receiving advertisement royalties from any brands. I have conducted biomedical research for which I have received research money from publicly-funded national research councils and medical charities, and also from private companies, including Novo Nordisk Foundation, AstraZeneca, Amylin, A.P. Møller Foundation, and Augustinus Foundation. I’ve also consulted for Boost Treadmills and Gu Energy on their research and innovation grant applications and I’ve provided research and science writing services for Examine — some of my articles contain links to information provided by Examine but I do not receive any royalties or bonuses from those links. These companies had no control over the research design, data analysis, or publication outcomes of my work. Any recommendations I make are, and always will be, based on my own views and opinions shaped by the evidence available. My recommendations have never and will never be influenced by affiliations, sponsorships, advertisement royalties, etc. The information I provide is not medical advice. Before making any changes to your habits of daily living based on any information I provide, always ensure it is safe for you to do so and consult your doctor if you are unsure.